The compound (6aR,9aS)-5,6a,7,8,9,9a-hexahydro-5-methyl-3-(phenylamino)-2-((4-(6-fluoropyridin-2-yl)phenyl)methyl)-cyclopent[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(2H)-one is disclosed in WO 2009/075784 (U.S. Pub. No. 2010/0273754). This compound has been found to be a potent and selective phosphodiesterase 1 (PDE 1) inhibitor useful for the treatment or prophylaxis of disorders characterized by low levels of cAMP and/or cGMP in cells expressing PDE1, and/or reduced dopamine D1 receptor signaling activity (e.g., Parkinson's disease, Tourette's Syndrome, Autism, fragile X syndrome, ADHD, restless leg syndrome, depression, cognitive impairment of schizophrenia, narcolepsy); and/or any disease or condition that may be ameliorated by the enhancement of progesterone signaling. This list of disorders is exemplary and not intended to be exhaustive.
The publication WO 2009/075784 generally discloses the compound (6aR,9aS)-5,6a,7,8,9,9a-hexahydro-5-methyl-3-(phenylamino)-2-((4-(6-fluoropyridin-2-yl)phenyl)methyl)-cyclopent[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(2H)-one in free base form and generally in pharmaceutically acceptable salt form. The monophosphate salt crystals of the compound (6aR,9aS)-5,6a,7,8,9,9a-hexahydro-5-methyl-3-(phenylamino)-2-((4-(6-fluoropyridin-2-yl)phenyl)methyl)-cyclopent[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(2H)-one (“the Compound”) is disclosed in U.S. Provisional Application No. 61/662,335. These applications, however, do not disclose specific crystals of the Compound in free base form and use of such free base crystals, which is now the subject of the current application.